Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare write (readOnlyHint=false), non-destructive, and closed-world, so the safety profile is covered elsewhere. The description adds only the ownership requirement; it says nothing about idempotency behavior despite a required idempotencyKey, nor about expectedVersion conflict handling, nor whether a forecast cost can later be converted to actual. For a mutating tool with 8 required parameters, that is a meaningful disclosure gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The single sentence is front-loaded and free of waste, which is good. But at one sentence for a 12-parameter mutation tool it is under-specified rather than appropriately sized, so the economy costs more than it saves.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be explained. Still, for a write tool with 8 required parameters at 0% schema coverage, the description omits idempotency, versioning, and field-level meaning that an agent needs to call it correctly, leaving it materially incomplete relative to the tool's complexity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% across 12 parameters, so the description must carry parameter meaning and it largely does not. Only the "actual or forecast" phrasing hints that actualCost is optional relative to the required quantity/unitCost fields; idempotencyKey, expectedVersion, itemType (the one enum), expenseDate, and trade are all left completely unexplained.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb ("Adds") and resource ("job cost") and scopes it to a single entry that may be actual or forecast, which separates it from sibling listers and creators like get_job_financials or create_job. It does not explicitly name any alternative tool, so differentiation from the draft/payment-preparation siblings rests on the resource noun alone.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase "to an owned job" implies a prerequisite (the caller must own the job), which is implicit guidance about when this call is valid. However, there is no statement of when to use this versus recording costs elsewhere, no mention of what to do on version conflicts, and no exclusions or alternatives offered.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.